In order to monitor sample water containing few impurities, such as water for medicine manufacturing, process water for semiconductor manufacturing, cooling water, boiler water, or tap water, TOC of such sample water is determined to quantify the amount of organic substances contained therein.
As a method for determining TOC, a method including the steps of: converting organic substances contained in sample water into carbon dioxide with an oxidation reactor, transferring the carbon dioxide into measurement water through a gas-permeable membrane, and determining the carbon dioxide concentration of the measurement water by measuring the conductivity of the measurement water containing the carbon dioxide transferred from the sample water with a conductivity meter is known (see Patent Documents 1 and 2).
As a method for measuring a conductivity caused by carbon dioxide to determine TOC, a method, in which a difference in the conductivity of sample water before and after oxidation is detected using at least two electrodes provided at positions where the conductivity of the sample water can be measured before and after oxidation, is disclosed (see Patent Document 3). An example of a TOC meter using such a method is A-1000 manufactured by ANATEL.
As a method for accurately determining the TOC content of water containing few impurities, such as water for semiconductor manufacturing or water for medicine manufacturing, with a relatively-compact apparatus, a method, in which organic substances contained in such water are decomposed by UV light into carbon dioxide and the carbon dioxide is separated by a carbon dioxide separation part to measure a conductivity, is known.    Patent Document 1: Japanese Patent No. 2510368    Patent Document 2: Japanese Patent Application Laid-open No. 2006-90732    Patent Document 3: Japanese Patent Application Laid-open No. 2001-281189